One of the better "versions" of psionics, or so I've heard. I've never really liked psionics, and this sourcebook didn't change opinion. In a world of magic, I just see psionics as unnecessarily more of the same.
This sourcebook starts off by explaining psionics and the new core classes. It moves on to feats, skills, and a few prestige classes (just a few unfortunately, so not a whole lot of options). Then follows a long list of powers, a lot of which are basically just psionic versions of common spells. There are a couple of interesting powers that are uniquely psionic in nature, but those are few. The sourcebook ends with a few monster entries with a psionics theme, none of which I found to be particularly inspired.
Basically, just feels like a typical sourcebook to me, like adding psionics as a variant spellcasting system. Nothing more than that. What would've made this sourcebook more "complete" would've been a chapter that thoroughly examines the role-playing and world-building options that includes or introduces psionics, instead of just a small section that talks about the options of interacting with conventional spells.